In chains used in abrasive environments, it is desirable to protect the wear surfaces comprised of the outside surfaces of the chain pins and the inside of the chain bushings by keeping these bearing surfaces lubricated and by preventing abrasive material from entering the space between the bearing surfaces. See for example, U.S. Pat. No. 4,464,151, issued to Kahl on Aug. 7, 1984, which is incorporated herein by reference.
A problem with prior art chain joint seals is that they wear quickly in certain applications such as when they are exposed to heat and very abrasive materials. For example, prior art chain joint seals wear quickly when used in material handling elevators where they are exposed to fine abrasive materials such as cement, ash, powdery metal (e.g. hot, dry, fine, powdery magnesium), or other materials. If the chain joint seal becomes worn, fine abrasive material can then enter into the chain joint and fill the space between the chain pin and a chain bushing, resulting in pin wear or dry cavitation-erosion type wear. This wear can limit chain life in a conventional chain.